Method of treating oil and gas wells



June 24, 1941. s.. M ZANDMER 2,246,611

METHOD oF TREATING on.. A1115 GAS WELLS' Filed Oct. 12, 1936 2 Sheets-Sheet 1 2 9 l 3o w 23 S 1 22 /0 L F3311 @a 1 l] V 23 .sA/vo June 24, l941 s. M. zANDMER METHOD OF TREATING OIL AND GAS WELLS Filed on. 12, 193s 2 Sheets-Sheet -2 INVENTOR ,5b/ Kyron Zaad/2z Patented June 24, 1941 -UNITED STATES -PATENT OFFICE METHOD OF TREATIN G OIL AND GAS WELLS Solis Myron Zandmer, Los Angeles, Calif. Application October 12, 1936, Serial No. 105,282

(Cl. IGZ-) 2 Claims.

My invention relates to the art of trea ng oil and gas wells. More particularly, my in ention relates to a method of opening up passageways 'in the desired zone.

Particularly is it a primary object of my inventionvto open up passageways for an apprecisive into the well bore and causing` it to go from.

the bore into the surrounding formation or country'rock, and detonating the explosive while in intimate contact with said country rock.

My invention will be setforth as applied to an oil well. However, it must be remembered that oil wells produce oil and gas in greatly vary- -ing ratios, and also that oil is derived from various formations, although generally oil is found in an upwardly arched geologicstructure which forms the trap for said oil. For purposes of greater deit'eness in illustrating and setting forth my invention, I will describe the same as applied to a type of oil bearing limestone structure actually encountered. My invention is applicable to wells of variable gas-oil ratios.

Oil and gas accumulations, in a eld in which limestone is a reservoir-rock, naturally are more has determined to a large extent the quantity of oil and gasv available to entry into the well bore. By the use of my invention I am now able to make these areas of porosity, which were previously isolated by more or lessA impervious areas, available for entrance to the well bore by opening up passageways to such isolated areas. Also by the use of my invention, I am able to open up interconnecting passageways in and to the less j pervious producing area,'so .that more 0r less nelydisseminated quantities of oil over extended areas, which would heretofore beunrecoverably held in the limestone formation, are now available for connection and entry into the well bore. Heretofore, the absence of sufficient fissures, avenues, openings, passageways and channels in the country rock immediately surrounding the well bore resulted in much of the oil in the producing formation not reaching the well bore. When such was encountered, very often chemical solutions were injected into the well to react with the producing formation to open up fissures and channels to permit the oil in the surrounding producing area to enter the well bore or well cavity.

The most common chemical method is that of acidizing. By this method, acid, such as hydrochloric acid where the formation is limestone, is pumped down tubing to the bottomcf the well. Here the acid, generally held under pressure, eats its way through the various channels present into the surrounding limestone/formation. New passageways are formed or the presently existing cracks or flssures are enlarged by the dissolving action of the acid until substantial channels are yformed in the producing formation, which chanchemicals, in taking the lines of least resistance,

tend to enlarge the already existing porosityv of the gas producing zone and do not substantiallyV 4cause openings through the more impervious limestone portion wherein the oil is located es'- pecially if large quantities of gas are present.

There may not be suilicient porosity in the I limestone surrounding the bore to permit the oil to flow into the well bore. However, the gas is invariably able to enter the bore even though the oil is held back by the relatively impervious character of the formation. It is the primary object .of this invention to provide a method for increasing the porosity of the area surrounding the well bore so that such oil in porous areas remote from the bore, as well as the oil in the less pervious area, will be tapped and drained to the well bore even though the oil be at substantial distances therefrom and/or even though the oil is in the so-called impervious limestone. i

Attempts have been made to use explosivesto open upthe formation surrounding the well, but

in such attempts, the use of explosives liasbeen confined to the well bore itself and not supplied to the country rock. The procedure in these attempts is to lower into the well anexplosive in cylinders or canisters and detonate such explosive in the well bore while so contained in such cylinders or canisters. The extent of the detonation is limited because of the limited quanwell production was not tity of explosive, which quantity is limited by the volume of the well bore opposite the productive zone to be treated. Likewise, the effect of the explosives is confined to the formation adjacent the Well bore and often fails to render the well more productive.

In this regard, let it be noted that quite often a nonproductive or non-commercial well has been drilled in a productive limestone oileld, said well being adjacent to or offsetting a large producing oil well. In many of these lcases, it has been impossible by detonating an explosive in the non-commercial wellbore to break or connect" up this dry bore with the productive areas feeding the large producing adjacent well, as shown by the resultant failure of the explosive action to make a commercial producer of the non-commercial well. By use of my invention, the explosive will be sent from the non-commercial well bore into the country rock before detonating said explosive, and hence be closer to said productive areas feeding the large producing well and consequently have that much better chance to tap this area by being exploded closer to said oil productive area.

The common practice in drilling oil wells is to provide the well bore with casing (usually from 4 to 12" in diameter) to a point above the producing formation and then cementing the casing at its lower end, i. e., seal oif communication betweem the bore and the space surrounding the casing above the lower end or shoe of the casing. Thereafter vthe drilling of the well is continued through the producing formation until the desired level is reached.

If the well is not productive or sufiiciently productive, one method which was heretofore used in attempting to increasethe production of a well was accomplished by the use of explosives. Explosives were lowered into the well bore and such explosives were exploded while in the well bore. This method is called shooting the well and in recent years has been substantially replaced by the acidizing process. The effect of the explosive Awas sometimes successful, but very often the action was local and no contact was made bethe acid tends to follow the more porous gas zone adjacent to the oil zone, and does not increase the oil productivity of the well.

In my invention I provide a method for placing and detonating an explosive in the surrounding formation, as distinguished from placing and detonating the explosive in the well bore itself, which results in greatly increasing the openings in the surrounding formation, despite the fact that such formation may be of the more solid and more impervious limestone. In other Words, whether the acid has produced'openings in the oil zone, or in the gas zone next to the oil zone, my invention provides for delivering explosive to and detonating the same in the said openings in the formation surrounding the well bore, thereby opening a flssuring system and hence a far greater drainage area is created and made available to the well.

In carrying out the above method, which is the subject matter of my invention, I'find that special provision must be made for lowering the explosive into the well bottom. The tubing which has been heretofore used for acidizing the well may not be used to introduce certain explosive into the well bottomV and from the Well. bottom into the formation surrounding the well. If it were attempted to introduce certain explosives into the well by means of the heretofore used steel tubing, there, of course, would be a thin film of the explosive adhering to the inside of the pipe "and in the interstices formed by the abutting tween the well bore and the more removed porous j In these cases the terially increased.

In recent years the most common and accepted commercial practice used if the well is not sufficiently productive is that known as acidizing,- this because fissures or passageways can be opened up at more distant points from the well bore by such practice, as an acid under pressure affects more distant areas than did an explosive detonatedin the well bore. The explosive which was detonated in the well bore failed to crackup or reach into the formationl which is distant from 'the well bore. In. applying the acidizing treatment to a well, ordinarily a tubing is let down inside the casing and reaches substantially the bottom of the well bore. 'This tubing is made from sections oi' pipe, such as two or three inch steel pipe and the various sections secured together by screw type couplings. The well is then filled with oil and 'then the acid is pumped under pressure down this tubing to the bottom of the well and the pressure held to permit the acid to eat its way through the surrounding limestone areas in 'the country ro k.

formation-and enlarge the existing cracks, open- Oftentimes this acidizing ends of the separate pipe sections as well as the threaded connections'between the pipe sections.- When the tubing so made up o f such sections would be attempted to be removed from the well bore, it would be necessary to unscrew lthe various sections which form the tubing. In this attempt. to unscrw such sections, the friction and heat created thereby would detonate explosives or at least would create -too dangerous a situation. Obviously, such a practice would be unworkable, with danger to life oi' the operators to the extreme. Parenthetically let it be remembered that the nitroglycerin containers, even after they have been most carefully emptied, contain sufficient particles left so that a bullet striking near the seam at the base of the can will explode the can.

The above mentioned general objects of my invention, together with others inherent in the same, are attained by the process and apparatus therefor illustrated in the following drawings, the same illustrating a. preferred exemplary form of application of my invention, throughout which drawings like reference numerals indicate like parts:

Figure 1 is a somewhat diagrammatic view in vertical section showing a well and a geological structure, with parts somewhat exaggerated for purpose ofl illustration, to which this invention may be applied;

Fig. 2 is a view similar to Figure 1, with the upper portion broken away, showing the geological structure after this invention has been applied thereto;

Fig. 3 is a somewhat diagrammatic view in vertical section,with parts brokenaway, of a well, showing a means for supporting therein a long flexible hose which would not be self supporting due to its great length;

Fig. 4 is a fragmentary vertical sectional view of the lower portion of a well showing therein a portion of a relatively long flexible hose which is reinforced, except for a section`of its lower end portion to render saidJ hose self-supporting where below the surface at which the casings are cemented, of course varies with each well. The drilling continues through the productive horizon or zone, which zone will vary in thickness with each individual well. Drilling may be continued through this zone until the well begins to produce gas and oil, or until it has beendetermined that sufficient productive formation has been drilled through to be included in a production test.

In illustrating my invention, I have indicated in the drawings the cap rock formation as at I3, and an oil producing limestone formation or country rock as at I4. In the limestone formation I have illustrated the upper pockets or relatively porous or gas producing area I5 and the lower relatively impervious oil producing area I6 in the country rock surrounding the well bore I'I.

In 'my invention the well may be chemically treated by any of the usual means, such as providing acid through the tubing IS, to mention only the most usual method, to enlarge or open up ssures and passageways and the well then cleaned of the acid and reaction products thereof. Thereafter, if they well is not properly producing, an explosive in accordance with my invention is introduced into the well bore Il.

well was cemented in the usual manner as at I2. The drilling was continued to approximately 5,017 feet, at which point Madison limestone formation was reached. In drilling into this limestone formation, a ow of gas was encountered. Upon continued drilling the gas flowsteadily increased until at the depth of 5,055 feet a ow of approximately two million cubic feet of gas per day resulted.

Albailer run into the well at this point bailed the rst oil encountered in the well, but the oil would not iiow from the well for the reason that the gas was above the oil and the gas merely entered the well and escaped without lifting the oil, which was present in such limited quantities that it did not rise to the gas level. The drilling continued until a-` depth of approximately 5,073 feet, and more oil continued to show, but still not enough to raise to the gas zone and be carried from the well by said gas. At this point the well was acidized in the usual manner in the vattempt to make the well commercially productive.

In acidizing, the entire well is lled with oil Y and then acid pumped down the tubing to the in the casing and in the tubing. This was done Before introducing the explosive into the well l bore, in most cases it is desirable to fill the bot-1 tom of the well bore I1 with a plugmember I8 back to the porous or gas area I5 thereabove, so that the explosive is not resting on .the well bottom, which may be near an underlying water horizon. The plug member I8 may be a material such as a tar product, which will be'readily later removable and will keep the explosive off the vwell bottom and thereby prevent breaking the well bottom down into the water table or level underlying the oil level. If the explosive to be used is nitro-glycerine, then the well is filled with a liquid, such as water, in which nltro-glycerine is relatively insoluble and which has a specific gravity sulciently less than the specic gravity of the nitro-glycerine so that the explosive will gently settle through it. Thereupon. a fluid explosive, as nitro-glycerine, is introduced into the well bore I1. The specific gravity of the nitroglycerine is such that by uid pressure the explosive may be gently floated down through the Water to the Well bore` I1 and thence into the fissures and cracks in the surrounding country rock I4. Thereupon, the explosive is detonated and due to the fact that the explosive is distributed substantially in the various fissures and openings, the explosion or detonation of the explosive will open up the producing zones I4, I5

and I6 land provide sufficient avenues s6 that oil and gas products in the said producing zones,

even at remote distances from well bore Il, will have access through these avenues to the well bore I'I and allow resultant oil and/or gas drainage to the said bore.

, As one example of the type of well in which my invention has application, the following is given:

A well was `drilled to approximately 4,900 feetv where shale was encountered. At this point the in the above mentioned Well, in which case 4,000 quarts of acid were forced out of the well bottom into the country rock.

After permitting the acid to remain in the surrounding strata for a few days, the oil in the tub-- ing was removed to a depth of approximately 1,800 feet, at which time the gas pressure forced the remaining column of oil out, and the well cleaned itself, and removed the acid and reaction products thereof.

The result of this acidizing job was that some acid had eaten into the producing area, which resulted in an increase of oil, (although not in commercial quantities) so that the gas now actually produced a continual spray of oil in flowing from the well. However, in so acidizing, the acid flowed from the bore, for the most part, to thel more porous gas producing area. I5, taking the` lines of least resistance and did not eat its way into the more solid and more impervious limestone country rock formation I4 and to the oil producing area I6, this being obvious from the factthat the gas production was considerably' increased and the oil production only slightly increased,

'I'he well was deepened through impervious limestone (as shown by the limestone samples recovered from this deepening operation) to 5,118 feet, i. e., about forty-five feet and a further slight showing of oil was encountered. The well was acidized again, but vit was found that in supplying 6,000 quarts of acid to the well that no pumping pressure whatsoever was required, whereas in the first acidizing process while using -less acid, the original pumping pressure had been as high as 1,000 pounds. This clearly indicated that the acid inthe second acidizing operation mainly reentered the original gas yielding zone I5 (said zone lying immediately over the oil zone I6) 'in which it had previously eaten channels. This further acidizing did not substantially increase the oil production of the well, as it .was not opening further channels, but merely flowing through the original channels which hadbeen created by the rst acidizing, i. e., the liquid was following lines of leest resistance.

In other words, at this point in the drilling and production of the well, the usual and commercially accepted method failed to open sumcient channels into the oil zone I6 or to increase the porosity to such an extent as to provide sufficient channels through the oil bearing zone I6, to the end of increasing the production to commercial quantities.

In connection with introducing the 6,000 quarts of acid in the above described second acid application, a quantity of oil amounting to 40 barrels (in excess of 6,000 quarts) was also introduced into the well and followed the acid out of the well bore I'I. Also more oil could have been introduced into the well without requiring appreciable pumping pressure. All these facts establish clearly that there was an extended area immediately adjacent to and above the oil zone I6 in that particular case. Such an extended area will permit the introduction of a like large quantity of explosive therein.

In general, my invention provides and employs an explosive in the country rock I4 surrounding the bore I1 to open up channels in the oil bearing strata at places of substantial distances from the well bore. In such a well as just described, the nitro-glycerine may be deposited in the well bore I1, which has been filled with water and the nitro-glycerine will gradually and gently settle by gravity to the bottom of the well. From the bottom of the well, the explosive will move by fluid pressure into the ssures and openings in the formation which may be those naturally there or those opened by a chemical processI such as acidizing. Upon detonation of such explosive, the porosity of the well is substantially increased and openings are made through the solid and more impervious limestone formations.

In my invention I employ a uid explosive in a mobile form, as nitro-glycerine, and by gravity and pressure force the explosive into the country rock I4 or formation surrounding the well bore and I detonate such explosive whileit is in the country rock. This may be accomplished by detonating an explosive in the well bore I 1, thereby causing a force to be transmitted to the explosive in the surrounding rock and detonating such explosive. This method results in opening up of fissures and openings 20, leading to the bore so that the production of a well may be increased far beyond that of anything accomplished by present methods. Of course, the tubing would be removed before detonation.

Ordinary well mechanics, which provides the necessary care in handling explosives so as to protect the casing and the equipment, as well as prevailing well mechanics, in general, are not detailed here. Proper care in putting the explosive by uid pressure into the formation will include holding the explosive in the bottom portion of the well bore II and not allowing it to rise into the casing. This protection is secured by having the space between the tubing I9 and casing I I filled with water and closed at the well top by valves or gates, or the removable screw plug 29, shown in the drawings, so that no explosive supplied to the bottom of the well can rise appreciably up the well bore I1, so as to rise to the level of the base of the casing.

By pumping water down the tubing at the end of the process of introducing the explosive to the formation, said explosive will be completely displaced from the tubing by pumping water down the tubing, measuring instruments being provided to indicate the proper uid volumes to accomplish this. By means of these accurate measurements and devices now in common practice in well boring to displace fluids in the well bore, all of the explosive will be in the country rock, except the small quantity which will be retained in the bottom portion of the bore, preferably in a sealed canister, so as to have in the bore only suicient explosive to detonate the charge in the country rock, but not enough to injure the casing.

In the foregoing I have illustrated the application of my invention to one well, but it is to be understood that I am not to be limited to any such speciilc application. There will be different conditions in the wells, which will determine the best method o f putting the explosive into the well bottom, and then from the well bottom into the country rock. In some instances it may be advisable to lower the explosive into the well bottom by lowering it in bailers with a valve on the bailers, so that the explosive will be released when the bailers reach the bottom of the well. Also in some wells it may be desirable to place the explosive in a container, such as a capsule. After the capsule is lowered into the well bore, the capsule may be dissolved by a suitable agent and the explosive will thereupon be released at the bottom of the well. In any vof the above methods. the explosive is located at the bottom of the well and from there it is forced into the surrounding country rock and exploded in the country rock.

In Fig. 3 I show a preferred construction where a continuous rubber tube 2l without joints is supported by a wire cable 22. The rubber tube is connected to said cable by a. clamp 30 connected with the rubber tube 2| and a connector means 23 connected with said clamp 30 and with the connector means 23. Thus there are no joints in which the explosive may lodge. A hose having joints between sections thereof, however, may be used as the hose is flexible and may be removed as a unit. 'Ihe cable 22 thus supports the weight of the rubber tube 2|. Otherwise the weight of the rubber tube involved in reaching the bottom of an oil well, such as'of 5,000 feet or more depth, might be excessive, so far as the strength of the material is concerned and involve undue strain of the rubber and breakage.

In Fig. 4 a exible tubing 24 is illustrated, which is reinforced by metal 25, such as wire. This character oi' tubing may be manufactured so as to be self-supporting, for use in great lengths for suspension in wells.

Either of these types oi' tubing 2l or 2l shown in Figs. 3 and 4 may be employed for introducing the explosive into the bottom of the well. 'Ihe explosive may be introduced into the well down such a tube. large drums and therefore will present no problem in removing.

In Fig. 5 a lining 28 is illustrated. which may be made ,from a phenol condensation product, or Bakelite. This lining would flt within the ywell casing, such as inside of the tubing I9, and would be made in sections, preferably corresponding in length to the lengths of the sections of the tubing I9. The unionof the sections o1' the lining 26 may be provided by having telescopically interfitted end portions 21 and 28, i. e., .the sections will have no threads and therefore there`will be no friction involved in removing these sections from each other, and at the same time this lining will serve to exclude the explosive from coming This tubing may' be provided on.

in contact with the threaded portions between the sections of steel tubing I9. By such means, a

lined steel tubing may be used and successfully removed from the well.

Obviously, changes may be made in the forms, dimensions and arrangement of the parts of my invention, without departing from the principle thereof, the above setting forth only preferred forms of embodiment.

I claim:

1. The method of increasing gas and oil production from a Well drilled in oil bearing limestone, comprising the step of introducing a chemical agent into the ssures in the surrounding country rock to increase the size of said fissures; the step of removing said chemical agent and the reaction products of said chemical agent with said country rock; the step of substantially lling the well bore with a liquid; the step of introduc' ing into said liquid an explosive in aliquid state, said explosive in the liquid state being characterized by having a specic gravity greater than said liquid inthe well bore, whereby the said explosive in the liquid state settles slowly down the well bore through the said liquid to the well bottom and thence llaterally into the ssures in the surrounding country rock; and the step of detonating said explosive in the fissures in the surrounding country rock.

2. The method of increasing oil and gas production from a well drilled in oil bearing zones, comprising drilling the well bore into the gas bearing strata positioned above the oil bearing strata; introducing a chemical agent into the ssures in the gas bearing strata to increase the size of said fissures; the step of removing said chemical agent and the reaction products of said chemical agents with the country rock forming said gas bearing strata; the step of substantially nlling the well bore with a liquid; the step of introducing an explosive in a liquid state into the liquid in the well bore, said explosive in the liquid state being characterized by having a specific gravity greater than said liquid in the well bore, whereby the explosive settles downwardly through the liquid to the bottom of the well bore and into the ssures in the gas strata; and the step of detonating said explosive in the ssures in the gas strata, whereby upon the detonation of said explosive openings are caused to extend from the oil bearing strata into the gas bearing strata.

SOLIS MYRON ZANDMER. 

